<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
        <!-- 2.html结构 -->
     <div id="app">
        <!-- 计数器功能区 -->
        <div class="input-num">
             <button @click="sub">-</button>
             <span>{{num}}</span>
             <button @click="add">+</button>
        </div>
     </div>
      <!-- 1.开发环境版本，包含了有帮助的命令行警告 -->
      <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
      <!-- 编码 -->
      <!-- 3.创建Vue实例 -->
      <script>
          var app=new Vue({
              el:"#app",
              data:{
                num:1
              },
              methods:{
                  add:function(){
                     //  console.log("add");
                     if(this.num<10){
                         this.num++;
                     }else{
                         alert("超过10啦");
                     }
                  },
                  sub:function(){
                     //  console.log("sub");
                     if(this.num>0){
                         this.num--;
                     }else{
                         alert("到底啦");
                     }
                  }
              }
          })
      </script>
 
</body>
</html>